Introducing the EXPRESS language family


EXPRESS is an information modelling language that has been powering what is now called "smart manufacturing". The language originated from the PDDI program, which was created in 1982 by the US Air Force at McDonnell Aircraft (now merged into Boeing).

The rasion-de-etre of EXPRESS is reflected in its name — to facilitate “expressiveness” in modelling information.

Today, EXPRESS is heavily used in advanced manufacturing, including in the industries of:

  • aerospace

  • automotive

  • construction

  • digital twins

  • smart manufacturing

Since then, EXPRESS has now grown into a family of information modelling languages, including EXPRESS-G, EXPRESS-I and EXPRESS-X, collectively referred to as the “EXPRESS language family”.

There are a few properties that separate EXPRESS from other information modelling languages:

  • It is a machine-readable language.

  • It is a data modelling language — not a programming language, even though it does provide algorithmic functionality

The EXPRESS language family

Each member of the EXPRESS family of languages provides specific functionality for the information modeller:

  • EXPRESS provides a lexical syntax for modelling information

  • EXPRESS-G provides a graphical syntax for modelling information, mirroring a subset of EXPRESS syntax

  • EXPRESS-I provides a lexical syntax for information model instances

  • EXPRESS-X provides a lexical syntax for mapping between information models

Standardization of EXPRESS

Given that EXPRESS was immensely useful for the manufacturing supply chain, it entered a standardization process at the National Bureau of Standards (now NIST) in 1984.

In 1986, EXPRESS was proposed by NBS to be an International Standard at ISO, which the language specification was ultimately published in 1994 as ISO 10303-11:1994.

In 1994, prior to its standardization, the first authoritative reference and manual on EXPRESS was published by Doug Schenck and Peter Wilson, the original inventor of EXPRESS and EXPRESS-G/EXPRESS-X respectively.

In 2004, the second edition of the language reference ISO 10303-11:2004 was published at ISO, with David Loffredo and Peter Wilson as its project leaders.